We present a dynamical study of the CL0023+0423 system at a redshift of z = 0.84 .
This system consists of two components separated in velocity space by \sim 2900 ~ { } { km~ { } s ^ { -1 } } and on the plane of the sky by \sim 0.23 ~ { } h ^ { -1 } ~ { } { Mpc } .
A kinematic analysis indicates that the two components are a poor cluster with a velocity dispersion of 415 ^ { +102 } _ { -63 } ~ { } { km~ { } s ^ { -1 } } and a mass of \sim 3 - 6 \times 10 ^ { 14 } ~ { } h ^ { -1 } ~ { } { M _ { \odot } } and a less massive group with a velocity dispersion of 158 ^ { +42 } _ { -33 } ~ { } { km~ { } s ^ { -1 } } and a mass of \sim 10 ^ { 13 } ~ { } h ^ { -1 } ~ { } { M _ { \odot } } ( Postman , Lubin & Oke 1998 ) .
The dynamics of galaxy groups at high redshift can provide important insights into the creation of present-day galaxy clusters .
Therefore , we have performed a dynamical study on this system in order to determine whether the two groups are infalling .
This analysis includes an analytic two-body calculation and N-body simulations .
The results of both studies indicate that the system is most likely not bound but simply a chance projection on the sky ; however , within the observational uncertainties , there do exist bound solutions where the two galaxy groups are currently moving toward each other and will eventually merge into a larger system of galaxies .
We have run one-thousand N-body simulations with random initial conditions based on the observed parameters of the CL0023+0423 groups .
A statistical analysis of these simulations indicates that there is an 20 % chance that the two groups will merge .
If the CL0023+0423 system does merge , it will appear as a cluster on the sky , as well as in velocity space , within 1 - 2 Gyrs .
The cluster will evolve dynamically for more than 3 Gyrs , appearing during this time more similar to an open , irregular cluster .
The final merged system has a velocity dispersion which is consistent with a local Abell richness class 1 cluster .

The morphological analysis of the galaxy populations of CL0023+0423 suggests that both groups are largely dominated by spiral galaxies .
Early-type fractions are 33 % or less ( Lubin et al .
1998 ) .
These modest early-type fractions have implications for both cluster formation and group evolution .
Studies of open clusters at z = 0.31 - 0.54 indicate that that they have early-type fractions between 45 - 80 \% ( Dressler et al .
1997 ; Andreon , Davoust & Helm 1997 ; Stanford , Eisenhardt & Dickinson 1997 ; Couch et al .
1998 ) .
If the CL0023+0423 system is the predecessor of such a cluster , the comparison may suggest that some fraction of early-type galaxies are formed between redshifts of z \sim 0.8 and z \sim 0.3 ; however , the morphological fractions are still highly uncertain .
In addition , the modest early-type fractions in both groups may be inconsistent with the strong correlation between velocity dispersion and early-type fraction observed in nearby groups of galaxies ( Zabludoff & Mulchaey 1998 ) .
Both groups apparently have relatively low early-type populations , irrespective of their velocity dispersion .
If the groups of CL0023+0423 are typical of galaxy groups at high redshift , and if high-redshift groups are the progenitors of local groups , this result may also imply that some early-type formation is occurring at redshifts of z \mathrel { \hbox { \raise 2.15 pt \hbox { $ < $ } \hbox to 0.0 pt { \lower 2.15 pt \hbox { $ \sim% $ } } } } 0.8 .
These results do not preclude the formation of early-type galaxies at very high redshift as many observations suggest ( e.g .
Steidel et al .
1996 ; Ellis et al .
1997 ; Stanford , Eisenhardt & Dickinson 1997 ; Postman , Lubin & Oke 1998 ) ; however , the observations of the CL0023+0423 system may imply that a fraction of the early-type population is forming and/or undergoing significant evolution at redshifts of z < 1 .